In “speakerphone” applications, the “near-talker” is the person using the speakerphone, and the “far-talker” is the person on the far end of the telephone line. The far-talker's speech is broadcast (played through a speaker) into the room (or other acoustic enclosure) that houses the speakerphone and the near-talker. An echo is produced by the far-talker's speech propagating through the room and being subsequently received at the microphone. Acoustic echo cancelers (AEC) are used to cancel the echo received at the microphone. The acoustic echo canceler is typically an adaptive filter that models the various echo paths in the room. Extreme cases exist where the acoustic echo canceler briefly fails to cancel the echo, such as prolonged double-talk or rapid near-talker movement. In these cases, a far-talker might hear a short burst of his/her own voice as an echo.
Residual echo suppression techniques attempt to remove the echo that remains after acoustic echo cancellation, thereby preventing the far-talker from hearing such bursts while still allowing the near-talker's voice to pass through undisturbed. Residual echo suppression techniques have been the subject of research, and papers have been published describing the work. Examples include: S. Gustafsson, et al., “Combined Acoustic Echo Control and Noise Reduction for Hands-Free Telephony,” Signal Processing, Vol. 64, pp. 21-32, 1998, hereinafter referred to as “Gustafsson;” and V. Turbin, et al., “Using Psychoacoustic Criteria in Acoustic Echo Cancellation Algorithms,”. Proc. IWAENC'97, London, pp. 53-56, September 1997, hereinafter referred to as “Turbin.” Despite ongoing research, current residual echo suppression techniques are not completely effective in removing residual echo.